1. Field of the Invention
This invention relates to the control of fluid flow in a pipe. In one aspect, this invention relates to subterranean pipes. In one aspect, this invention relates to pipes containing gaseous fluids at high pressure (greater than about 60 psig). In another aspect, this invention relates to a method and apparatus for interrupting fluid flow in subterranean pipes. In yet another aspect, this invention relates to repair of subterranean pipes from above ground.
2. Description of Related Art
The repair of fluid transmitting subterranean pipes is an ongoing necessity and typically requires access to the pipe, preferably without excavation of the surrounding area, an opening into the pipe, and some means of interrupting the fluid flow within the pipe to enable the necessary repair without fluid escaping from inside the pipe. Such repairs may include eliminating a leak, replacing a section of pipe, or replacing auxiliary equipment, such as gas meters.
The use of inflatable gas pipe stoppers or bags for interrupting the flow of gas through a pipeline or service line is well established. Such stoppers are typically employed for temporarily interrupting the flow of gas (or water) through the pipeline or service line while repairs to the pipeline or service line are effected. See, for example, U.S. Pat. No. 1,760,750 to Goodman which teaches a flexible inflatable stopper for gas and water mains that forms a complete closure for the main. In addition, if the stopper buckles or otherwise becomes deformed upon insertion, the placement of the closure will not be prevented. U.S. Pat. No. 1,946,138 to Gardner teaches a pneumatic stopper for a gas pipe including an air bag for stopping the pipe. The device includes a tubular housing and an inflatable bag, interconnected with an air tube which extends within the tubular housing. The air tube and bag may be moved downward with respect to the tubular housing to extend into the pipe after the housing has been threadably attached to the pipe. The air bag may then be inflated to stop flow within the pipe. And, U.S. Pat. No. 3,824,864 to Reigel et al. teaches a line stopper comprising a housing that is mountable to a conventional pipe tapping machine and a bag insertion assembly mounted in the housing. The insertion assembly includes a slidable insertion tube and an inflatable bag connected at the lower end thereof. The bag includes a rigid neck connected by a knuckle means to the insertion tube to enable the bag to be pivoted into the pipe. The housing is secured to the valve assembly by two pairs of ears which extend outward from the base and which are clamped to the valve assembly by bolts. When the bag is placed in the pipe, the insertion tube covers the edge of the hole in the pipe to prevent abrasion between the bag and the edge of the hole in the pipe.
In the natural gas industry, present day pipe flow stopping equipment is substantially the same equipment that the industry has been using for the last 50 years. The equipment is heavy, requiring multiple people or mechanical assists to maneuver, costly to maintain, and very time consuming when installing necessary fittings. Thus, new pipe stopping equipment that can address these problematic issues, while providing the same assurance of safety and performance, could save significant time and money during day to day operations.
Vintage plastic piping systems such as Aldyl-A and PVC materials require an alternative to squeeze-off and other stop-off means because many of these materials cannot or should not be squeezed to control the flow.
Another area of need is cast iron pipe systems that operate at pressures greater than about 5 psig. Current bag stopping equipment can only be used up to 5 psig. As a result, when cast iron systems are operating at higher pressures, the pressure in the system must first be lowered to less than 5 psig to enable conventional stopper bags to be employed. One alternative to lowering the pressure in such pipes is to use traditional stopping equipment and install heavy and expensive mechanical fittings that typically require reinforcement under the pipe to minimize the risk of future pipe breaks. However, both of these options require the use of larger excavations.